Sheep believed to be resistant to scrapie are succumbing to atypicalinfections and a newly identified strain of the disease. Eradicationprogrammes based on selective breeding should be reappraised.

Scrapie is a fatal brain disease of sheepand goats and is part of the transmis-sible spongiform encephalopathy(TSE) family. This family also includeschronic wasting disease of deer, bovinespongiform encephalopathy (BSE) in cattleand variant CreutzfeldtIakob disease inhumans. Unlike these relative newcomers,however, scrapie has been present for morethan 250 years in European sheep flocks andhas spread to many other parts of the world'.

In the 1990s, a proportion of sheep werefound to be genetically resistant to scrapie"'and, consequently, many countries haveestablished programmes to create disease-resistant national flocks by selective breeding.This new and unusual approach to diseasecontrol needs urgent reappraisal, however, asrecent discoveries in Europe suggest that theselected sheep might be susceptible to strainsof the disease that arise in the future. Atypicalforms of scrapie have been reported in'resistant' sheep in Germany3, Portugal4 andFrance'5. And a recently discovered strain ofscrapie, called Nor98, is now being detectedin several European countries. Writing inJournal of General Virology, Mourn and co-workers6 show that this strain primarilyaffects sheep that rarely succumb to conven-tional scrapie; conversely, typically'suscepti-ble' sheep seem to be unaffected.

The European Union (EU) is aiming toeradicate scrapie from its member stateswith a combination of two approaches. Thefirst, which has been compulsory since Oct-ober 2003, involves eliminating the diseasefrom currently infected flocks by cullingentire flocks, or by genetic testing and cullingof susceptible animals (Commission Regu-lation 1915/2003). The second approach,which will become compulsory from April2005, has the goal of reducing the chance thatuninfected flocks will become infected in thefuture (Commission Decision 2003/100/EC).As a minimum, rams intended for breedingin scrapie-free flocks of'high genetic merit'must be genetically tested, and those whose

genes suggest a susceptibility to scrapie willbe culled, despite being uninfected. Thisapproach targets rams because the relativelysmall number used for breeding provides afast means of spreading scrapie-resistantgenes through the sheep population. Bene-fits are expected to filter gradually into flocksof lower genetic merit.

In some countries, broadly similar con-trol programmes have been in operation forseveral years. For example, in July 2001 theUK government launched the NationalScrapie Plan for Great Britain', which, untilthe commission regulations came into force,used the same two-faceted approach but on avoluntary basis. In the United States, how-ever, genetic testing is used to eliminate dis-ease in scrapie-infected flocks, but breedingprogrammes involving scrapie-free flocks donot have to be based on scrapie genetics'. It'simportant to get the strategy right: nationalprogrammes to create scrapie-resistantflocks require the continued goodwill of the

sheep industry, and are expensive. For exam-ple, more than one million UK sheep havebeen genetically tested, at a cost of £19 mil-lion (US$37 million), during the first threeyears of Britain's National Scrapie Plan8, and£27.5 million has been allocated for this bythe UK government for the next three years.

Whether or not a sheep can succumb toscrapie is determined by the sequence ofamino acids that form its prion protein,which is encoded by its PrP gene. Five vari-ants (called haplotypes) of the PrP gene areknown to affect susceptibility. Sheep thatinherit the ARR haplotype from both par-ents (ARR/ARR) have the greatest resistanceto conventional scrapie2. Conversely, sheepinheriting the VRQ haplotype from bothparents (VRQ/VRQ) are extremely suscepti-ble2 to conventional scrapie and, in someinfected flocks, all such animals would beexpected to die from the disease. Fifteentypes of sheep are definable on the basis ofthe pair of PrP haplotypes inherited fromtheir parents; the extent to which they suc-cumb to scrapie, as reported in the UnitedKingdom, is shown in Figure 1. CommissionDecision 2003/100/EC aims to increase thefrequency of the ARR haplotype and elimi-nate the VRQ haplotype.

A fundamental assumption of selectivebreeding programmes is that 'resistant'sheep really are, and will remain, resistant toscrapie. But this assumption is now beingchallenged by the new findings3-6 emergingfrom mainland Europe. In 2002, many EUmember states began large-scale testing ofsheep in abattoirs for scrapie, using BSE-detection methods. This surveillance has,inevitably perhaps, revealed that scrapie ismore widespread than previously believed. Ithas also uncovered 'atypical' types9. Thesediffer from conventional scrapie in severalways, such as the pattern of deposition inthe brain of the abnormal form of the prionprotein.

graph/chart not available...TSS

Figure 1 Scrapie risks. Variations in the PrP gene determine the susceptibility of sheep to scrapie. Inthe United Kingdom, sheep with the VRQ variant (haplotype) are most at risk of succumbing to conventional (UK) scrapie. These sheep appear, however, to be resistant to the new Nor98 strain, from which sheep with the AHQ haplotype are instead most at risk. For each genetic type, 'risk' is theproportional representation in reported scrapie cases, divided by the proportional representation inthe national flock (UK) or flock mates (Nor98). Data are from rets 1,6.

Importantly, a few of the atypical casesare in 'resistant' sheep. Thus, Buschmannand co-workers' reported two atypical casesof scrapie in sheep of the ARR/ARR type inGermany, and Orge and co-workers4describe a third in Portugal. Three furthercases have been reported in France5. Thesediscoveries confirm, under natural con-ditions, a finding made in sheep experimen-tally inoculated with BSE: ARR/ARR sheepare not, after all, totally resistant to TSEs10.

These atypical scrapie cases show somesimilarity to a new strain of scrapie, firstdetected in Norway in 1998 (ref. 11). Moumand co-workers6 have now genetically testedall 38 Norwegian Nor98 cases, as well as theunaffected sheep in the flocks from whichthey came, allowing the relative susceptibilityor resistance of each genetic type to be esti-mated. The results transform our under-standing of the relationship between PrPhaplotype and scrapie. Sheep that are themost susceptible to conventional scrapieappear to be unaffected by Nor98 (Fig. 1).Conversely, susceptibility to Nor98 is linkedto the AHQ haplotype, which is generallyassociated with resistance (or, at most,low susceptibility) to conventional scrapie.Nor98 is also being identified over a widerarea in Europe. It has been reported inNorway, Sweden, Finland and, in November2004, in Ireland12 and Belgium13.

Encouragingly, there have been no casesamong ARR/ARR sheep, and so it is possiblethat national flocks of this genetic type maybe resistant to both conventional and Nor98scrapie. A warning shot has, however, beenfired. The existence of Nor98 shows thatsheep largely resistant to 'known' strains ofscrapie might be highly susceptible to a novelstrain identified in the future; and the dis-covery of atypical infections in ARR/ARRsheep presses the point that we cannotexclude these sheep from this risk. Largerepidemics of scrapie tend to be associatedwith flocks that have high proportions ofsheep susceptible to the local scrapie strain.Accordingly, as the ARR haplotype increas-ingly dominates European sheep popula-tions, there is a danger that epidemics ofa strain able to attack this haplotype couldbe larger than those the region has experi-enced in the past.

One final point: the existence of the VRQhaplotype has been enigmatic, as it is notknown to confer any benefits, but is oftenfatal for sheep exposed to conventionalscrapie. Why has it not been eliminated fromsheep populations by natural selection? Thefindings of Moum et al6 raise the possibi-lity that this haplotype exists today becauseit conferred resistance to past strains. If so,this is a strong argument for the preserva-tion of haplotype diversity in sheep popula-tions, and the long-term control of scrapiein Europe may be better achieved by theUS approach: eliminating infection with-in infected flocks and their contacts,while preserving haplotype diversity at anational scale.

5. Report on the Monitoring and Testing of Ruminants for thePresence of Transmissible Spongiform Encephalopathy (TSE) inthe EU in 2003, Including the Result of the Survey of PrionProtein Genotypes in Sheep Breeds. rep. 04-D-420525(European Commission Health & Consumer ProtectionDirectorate-General, Brussels, 2004).

6. Moum, T. et al. Gen. Virol. doi: 10.1099/vir.0.80437-0 (2004)

7. National Scrapie Plan for Great Britain. Schemes Brochure(Department for Enviroment, Food and Rural Affairs,London, 2001)

8. National Scrapie Plan. Consultation on the Strategic Review(Department for Environment, Food and Rural Affairs,London, 2004).

Kuru and Creutzfeldt-Jakob disease of humans and scrapie disease of sheep and goats were transmitted to squirrel monkeys (Saimiri sciureus) that were exposed to the infectious agents only by their nonforced consumption of known infectious tissues. The asymptomatic incubation period in the one monkey exposed to the virus of kuru was 36 months; that in the two monkeys exposed to the virus of Creutzfeldt-Jakob disease was 23 and 27 months, respectively; and that in the two monkeys exposed to the virus of scrapie was 25 and 32 months, respectively. Careful physical examination of the buccal cavities of all of the monkeys failed to reveal signs or oral lesions. One additional monkey similarly exposed to kuru has remained asymptomatic during the 39 months that it has been under observation.

12/10/76AGRICULTURAL RESEARCH COUNCILREPORT OF THE ADVISORY COMMITTE ON SCRAPIEOffice NoteCHAIRMAN: PROFESSOR PETER WILDY

snip...

A The Present Position with respect to ScrapieA] The Problem

Scrapie is a natural disease of sheep and goats. It is a slowand inexorably progressive degenerative disorder of the nervous systemand it ia fatal. It is enzootic in the United Kingdom but not in allcountries.

The field problem has been reviewed by a MAFF working group(ARC 35/77). It is difficult to assess the incidence in Britain fora variety of reasons but the disease causes serious financial loss;it is estimated that it cost Swaledale breeders alone $l.7 M duringthe five years 1971-1975. A further inestimable loss arises from theclosure of certain export markets, in particular those of the UnitedStates, to British sheep.

It is clear that scrapie in sheep is important commercially andfor that reason alone effective measures to control it should bedevised as quickly as possible.

Recently the question has again been brought up as to whetherscrapie is transmissible to man. This has followed reports that thedisease has been transmitted to primates. One particularly luridspeculation (Gajdusek 1977) conjectures that the agents of scrapie,kuru, Creutzfeldt-Jakob disease and transmissible encephalopathy ofmink are varieties of a single "virus". The U.S. Department ofAgriculture concluded that it could "no longer justify or permitscrapie-blood line and scrapie-exposed sheep and goats to be processedfor human or animal food at slaughter or rendering plants" (ARC 84/77)"The problem is emphasised by the finding that some strains of scrapieproduce lesions identical to the once which characterise the humandementias"

Whether true or not. the hypothesis that these agents might betransmissible to man raises two considerations. First, the safetyof laboratory personnel requires prompt attention. Second, actionsuch as the "scorched meat" policy of USDA makes the solution of theacrapie problem urgent if the sheep industry is not to suffergrievously.

snip...

76/10.12/4.6

http://www.bseinquiry.gov.uk/files/yb/1976/10/12004001.pdf

http://www.bseinquiry.gov.uk/files/yb/1976/10/12002001.pdf

==========================================

Release No. 0141.02

Ed Curlett (301) 734-3256Jerry Redding (202) 720-6959

TESTING TO CONTINUE ON IMPORTED SHEEP CONFISCATED LAST YEAR

WASHINGTON, April 11, 2002 -- The U.S. Department of Agriculture today announced that tests conducted on a flock of sheep confiscated last year from a farm in Vermont confirm that two of the 125 sheep tested positive for an atypical undifferentiated transmissible spongiform encephalopathy (TSE) of foreign origin. The flock of 125 sheep was confiscated in March 2001 after four animals from an associated flock tested positive for TSE in July 2000. USDA will continue to conduct additional tests to determine the type of TSE in these sheep.

"These results confirm our previous conclusions were correct and that we took the appropriate preventative actions in confiscating these animals," said Bobby Acord, administrator of USDAs Animal and Plant Health Inspection Service. "USDAs actions to confiscate, sample and destroy these sheep were on target. As a result of our vigilance, none of these confiscated animals entered the animal or human food supply."

The sheep, imported from Belgium and the Netherlands in 1996, were placed under certain federal restrictions when they entered the country as part of USDA's scrapie control efforts. In 1998, USDA learned that it was likely that sheep from Europe were exposed to feed contaminated with bovine spongiform encephalopathy. At that time, the state of Vermont, at the request of USDA, imposed a quarantine on these flocks, which prohibited slaughter or sale for breeding purposes.

On July 10, 2000, several sheep from the flock tested positive for a TSE, a class of degenerative neurological diseases that is characterized by a very long incubation period and a 100 percent mortality rate in infected sheep. Two of the better known varieties of TSE are scrapie in sheep and BSE in cattle. There is no evidence that scrapie poses a risk to human health.

On July 14, 2000, USDA issued a declaration of extraordinary emergency to acquire the sheep. This action was contested by the flock owners. A federal district court judge ruled in favor of USDA based on the merits of the case. The flock owners appealed to the Second Circuit Court requesting a stay, which was denied. The sheep were confiscated by USDA in March 2001 and transported to USDA's National Veterinary Services Laboratories in Ames, Iowa, where they were humanely euthanized. Tissue samples were collected from the sheep for diagnostic testing and USDA will continue with additional tests which could take up to 2 - 3 years to complete. In all, USDA has acquired 380 sheep from a total of three flocks. All of the animals were humanely euthanized, sampled and disposed and did not enter the animal or human food supply.

Our goal continues to be to prevent, detect and eradicate foreign animal diseases to protect American agriculture, natural resources and consumers," said Acord. "We will continue to utilize the scientific results of these and other tests conducted during the last several years to strengthen our extensive surveillance, monitoring and prevention efforts."

For more information about USDAs ongoing surveillance, monitoring and prevention efforts as it relates to this situation, please visit www.aphis.usda.gov/oa/tse/index.html

#

-------- Original Message --------

Subject: Sheep

Date: Sat, 12 Jun 2004 14:26:04 EDT

From: LAVET22@aol.com

To: flounder@wt.net

Mr. Singeltary. I hope this finds you well. As you are aware I left the USDA last year. I can only update you on the sheep before that time. Contact was established with the UK on doing the bioassay studies. They agreed. However, we were prioritized after their own needs, hence the delay. I am aware that there are now additional labs in Europe running the mouse bioassay strain typing. You will have to contact USDA for further word. Linda Detwiler

=========

My reply to Dr. Detwiler;

-------- Original Message --------Subject: Re: Sheep

Date: Sat, 12 Jun 2004 13:53:57 -0500

From: "Terry S. Singeltary Sr."

To: LAVET22@aol.com

References: <54.2bd2ac1e.2dfca4bc@aol.com>

hello Dr. Detwiler,

thanks for your kind reply.

> However, we were prioritized after their own needs, hence the delay. not sure i understand that? > You will have to contact USDA for further word. already done that, and there answer was; >5/20/04 > >Dear Mr. Singeltary, > >The Western blot tests on these animals were completed in April of this >year. That means that we can begin the mouse inoculations. To get the >results of the Western blot tests, you will need to submit a Freedom of >Information Act request through our FOIA office. The FAX number there is >301-734-5941. > >Have a nice day, > >Jim Rogers >APHIS LPA >and with my previous attempts for information via the FOIA through this administration (as you are probably very well aware of) they have all been ignored/refused. so any further attempts would be fruitless i am sure. thanks anyway...

I had signed up for the meeting and wanted to ask a question, but it tookme too long to finally get everything working properly on my end withthe viewing. finally got things going today and got into the audio of themeeting (will have to download an upgrade for my windows media).

ASIDE from the disturbing points made about sCJD not being tiedto BSE from some unpublished mouse bioassays (if i heard that right)and the fact that they still today base the increase of sporadic CJD inknown BSE countries as a happenstance of better surveillance, I wishto kindly ask a question not pertaining to the above, as disturbing asit is (lost my mother to the hvCJD 12/14/97) and i simply have neveraccepted the spontaneous/sporadic aspects of this agent in 85%+ ofall humans. never will, it's a pipe dream thought up in some back roomin the 80s to protect the industries involved (my opinion).

MY question is one about the VERMONT USA SHEEP that wereimported to the USA from Belgium and confiscated by the USDA severalyears ago due to an atypical TSE, with the announcement that mousestudies would be immediately started. I was informed by Dr. LindaDetwiler that it was DEFRA that was responsible for these mouse studiesbeing put on hold for 2 years.

WHY were such important studies put off for 2 years by DEFRA?

HERE is my correspondence with Dr. Detwiler;

Release No. 0141.02

Ed Curlett (301) 734-3256Jerry Redding (202) 720-6959

TESTING TO CONTINUE ON IMPORTED SHEEP CONFISCATED LAST YEAR

WASHINGTON, April 11, 2002 -- The U.S. Department of Agriculture todayannounced that tests conducted on a flock of sheep confiscated last yearfrom a farm in Vermont confirm that two of the 125 sheep tested positivefor an atypical undifferentiated transmissible spongiform encephalopathy(TSE) of foreign origin. The flock of 125 sheep was confiscated in March2001 after four animals from an associated flock tested positive for TSEin July 2000. USDA will continue to conduct additional tests todetermine the type of TSE in these sheep.

"These results confirm our previous conclusions were correct and that wetook the appropriate preventative actions in confiscating theseanimals," said Bobby Acord, administrator of USDAs Animal and PlantHealth Inspection Service. "USDAs actions to confiscate, sample anddestroy these sheep were on target. As a result of our vigilance, noneof these confiscated animals entered the animal or human food supply."

The sheep, imported from Belgium and the Netherlands in 1996, wereplaced under certain federal restrictions when they entered the countryas part of USDA's scrapie control efforts. In 1998, USDA learned that itwas likely that sheep from Europe were exposed to feed contaminated withbovine spongiform encephalopathy. At that time, the state of Vermont, atthe request of USDA, imposed a quarantine on these flocks, whichprohibited slaughter or sale for breeding purposes.

On July 10, 2000, several sheep from the flock tested positive for aTSE, a class of degenerative neurological diseases that is characterizedby a very long incubation period and a 100 percent mortality rate ininfected sheep. Two of the better known varieties of TSE are scrapie insheep and BSE in cattle. There is no evidence that scrapie poses a riskto human health.

On July 14, 2000, USDA issued a declaration of extraordinary emergencyto acquire the sheep. This action was contested by the flock owners. Afederal district court judge ruled in favor of USDA based on the meritsof the case. The flock owners appealed to the Second Circuit Courtrequesting a stay, which was denied. The sheep were confiscated by USDAin March 2001 and transported to USDA's National Veterinary ServicesLaboratories in Ames, Iowa, where they were humanely euthanized. Tissuesamples were collected from the sheep for diagnostic testing and USDAwill continue with additional tests which could take up to 2 - 3 yearsto complete. In all, USDA has acquired 380 sheep from a total of threeflocks. All of the animals were humanely euthanized, sampled anddisposed and did not enter the animal or human food supply.

Our goal continues to be to prevent, detect and eradicate foreign animaldiseases to protect American agriculture, natural resources andconsumers," said Acord. "We will continue to utilize the scientificresults of these and other tests conducted during the last several yearsto strengthen our extensive surveillance, monitoring and preventionefforts."

For more information about USDAs ongoing surveillance, monitoring andprevention efforts as it relates to this situation, please visitwww.aphis.usda.gov/oa/tse/index.html

#...end/

NOW, June 2004 those same test that we were told would start in2002, have yet to be started. THE TSE those VERMONT sheepwas supposedly to have had, has yet to be confirmed.

I hope this finds you well. As you are aware I left the USDA lastyear. I can only update you on the sheep before that time. Contact wasestablished with the UK on doing the bioassay studies. They agreed.However, we were prioritized after their own needs, hence the delay. Iam aware that there are now additional labs in Europe running the mousebioassay strain typing. You will have to contact USDA for further word.

Linda Detwiler=========

>However, we were prioritized after their own needs, hence the delay.

IF this was the case, this is totally unacceptable. FOR something thathas been ongoing since the 80s (BSE in SHEEP/GOATS) yet still unresolved,there is absolutely no excuse why these studies were put off. with the other sheepbrain mix-up and now the BSE in the French Goat, I find it very disturbing that theVermont Sheep studies were put off for 2 years for whatever reason, especiallywith the findings Dormont*, and Jean-Philippe Deslys* et al, that The agentresponsible for French iatrogenic growth hormone-linked CJDtaken as a control is very different from vCJD but is similar to thatfound in one case of sporadic CJD and one sheep scrapie isolate;

http://www.pnas.org/cgi/content/full/041490898v1

YES, i am still very angry, but i want to still thank SEAC for the workthey have done, i only wish things would go much faster and that theBSE/nvCJD only theory would be put to rest once and for all. Sciencehas pretty much proven that it was a pipe dream, however sciencedoes not have near as much to do with this mess anymore as theindustry and politics do. it's simply not about science anymore.IN the USA, you dont even hear of these new studies from theGov. and very little from the media...

As of September 30, 2004, there were 67 scrapie infected and source flocks (figure 3 ). There were a total of 100** new infected and source flocks reported for FY 2004 (figure 4 ). The total infected and source flocks that have been released in FY 2004 are 77 (figure 5 ). The percent of new infected and source flocks cleaned up or on clean up plans was 96%. In addition, as of September 30, 2004, 368 scrapie cases have been confirmed and reported by the National Veterinary Services Laboratories (NVSL) in FY 2004, of which 54 were RSSS cases (figure 6 , and figure 7 ). Thirteen cases of scrapie in goats have been reported since 1990 (figure 8 ). One new goat case was reported in FY 2004. New infected flocks, source flocks, and flocks released for FY 2004 are depicted in chart 4 . One new goat case was reported in FY 2004. Approximately 3,058 animals were indemnified comprised of 47% non-registered sheep, 44% registered sheep, 6% non-registered goats and 1% registered goats.

Scrapie: Ovine Slaughter Surveillance (SOSS)

The Center for Epidemiology and Animal Health (CEAH) released the results of the Phase II: SOSS study http://www.aphis.usda.gov/vs/ceah/cahm/Sheep/sheep.htm. The objective of SOSS was to estimate the national and regional prevalence of scrapie in mature cull ewes. Prior to the SOSS study, the prevalence of scrapie in the United States was estimated to be 0.07 percent (based on information from NAHMS Sheep 96, unpublished data). The SOSS study estimate for the national prevalence in mature ewes is 0.20 percent. The prevalence phase of the SOSS study started April 1, 2002, and continued through March 31, 2003. During this time period, samples were collected from 12,508 mature sheep at 22 slaughter facilities, as well as a major livestock market.

Of the 12,508 sheep tested, 33* were found to be scrapie positive: 27 black face; 3 mottled face; 1* white face; and 2 of unknown face color. Note: The raw prevalence is higher than the weighted prevalence. The difference is the result of weighting each positive based on the number of sheep sampled and the number of sheep killed at each plant.

Regulatory Scrapie Slaughter Surveillance (RSSS) RSSS started April 1, 2003. It is a targeted slaughter surveillance program which is designed to identify infected flocks for clean-up. Samples have been collected from 34,661 sheep since April 1, 2003, of which results have been reported for 28,677. Samples have been submitted from 42 plants (figure 9 ). The state identified on the tag of sampled animals is shown in figure 10 . There have been 77 NVSL confirmed positive sheep. There have been 54 NVSL confirmed positive cases in FY 2004. Face colors of these positives were 46 black, 6 mottled, and 2 white. The Six Month Rolling Average of Percent Scrapie Positive Black and Mottled Faced Sheep is shown in chart 6 . The number of RSSS samples collected by month**, region and total in FY 2004 are shown in chart 7 .

As of September 30, 2004, 90,322 sheep and goat premises have been assigned identification numbers in the Scrapie National Generic Database. Official eartags have been issued to 64,040 of these premises.

NOTES:*This number was decreased by one case as a result of a clerical error compared to the FY 2003 annual report.**Differences appear between this report and the September 2004 report due to late reporting of RSSS testing and quality review of status data As of May 2004 we are reporting only NVSL confirmed positive cases.